Vehicle seat having resilient suspension and constant acting damping means

ABSTRACT

A vehicle seat of the resiliently suspended type for use with earth working or agricultural implements or the like and wherein the seat itself is mounted on a parallel arm linkage arrangement and can be vertically adjusted to different heights. The seat furthermore has an air spring or the like for resiliently suspended the seat for a cushioning effect, which cushioning means can be locked out to provide a solid ride. In addition the seat has a damping means for providing a selectable stiffness or softness of the ride. This damping means is so constructed and arranged that it acts with essentially constant force on the seat regardless of the type of ride selected so that a constant force is applied by the damping means regardless of the vertical position to which the seat bounces or swings. Means are also provided for easily adjusting the vertical position of the seat so as to accommodate operators of different size.

Unite States atet n91 Swenson et al.

[ 1 VEHICLE SEAT HAVING RESILIENT SUSPENSION AND CONSTANT ACTING DAMPINGMEANS [75] Inventors: Richard F. Swenson; John J. Gryga,

Jr., both of Milwaukee, Wis.

[52] US. Cl. .297/300, 248/372, 248/399 [51 ..A47c 3/38, B60n 1/02 [58]Field of Search ..297/285, 300, 307-309;

[56] References Cited UNITED STATES PATENTS 3,519,240 7/1970 Swenson..248/399 3,356,413 12/1967 Radke et al. ..297/300 3,325,136 6/1967Radke et al. ..248/4()O 3,558,094 l/l97l Radke .248/400 4 1 Apr. 17,1973 Primary Examiner-Casmir A. Nunberg Att0rney-lames E. Nilles [57]ABSTRACT A vehicle seat of the resiliently suspended type for use withearth working or agricultural implements or the like and wherein theseat itself is mounted on a parallel arm linkage arrangement and can bevertically adjusted to different heights. The seat furthermore has anair spring or the like for resiliently suspended the seat for acushioning effect, which cushioning means can be locked out to providea'solid ride. in addition the seat has a damping means for providing aselectable stiffness or softness of the ride. This damping means is soconstructed and arranged that it acts with essentially constant force onthe seat regardless of the type of ride selected so that a constantforce is applied by the damping means regardless of the verticalposition to which the seat bounces or swings. Means are also providedfor easily adjusting the vertical position of the seat so as toaccommodate operators of different size.

19 Claims, 16 Drawing Figures PATENTEDAPR '3'. 727. 974

SHEET 1 UF 8 I. INVENTORS! RICHARD F. SWENSON 9 a 11 o BY uo/m J. ewe/gmA'ffcRuEY vii/z SHEET 2 BF 8 PATENTEBAPR 1 (I973 INVENTORS. RICHARD FTSWENSON JOHN J. GRVGA, .72. BY. W a m Affonh EY PATENTEUAPR 1 m '3; 727.974

SHEET 3 BF 8 JNVENTORS. RICHARD F. SWENSON JOHN J. GRYGA, .72. BY.

ITTORNEY PATENTEI] APR 1 H973 2 974 SHEET 1 [1F 8 INVENTORSZ RICHARD F.SWENSON BY. JOHN J. ewe/1 2.

PATENTED APR 1 7 I973 SHEET 5 OF 8 IN VEN TORS l RICHARD F SWENSON aomvJ. GRYGA, J2.

PATENTEBAPR 1 H973 SHEET 6 BF 8 IN VEN TORS. RICHARD F SWENSON JOHN J.GRYGA, J2,

Arrow/v5) PAIENTEI] APR 1 7 ms SHEU 7 OF 8 IN V EN T 0R5 RICHARD ESWENSON JOHN J. GRYGA, me.

PATENTEBAPR 1 7197s 5,727; 974

SHEET 8 BF 8 F -5/ Ac r-J INVENTORS. RICHARD F. swewsoN JOHN J. GRYGAme,

VEHICLE SEAT HAVING RESILIENT SUSPENSION AND CONSTANT ACTING DAMPINGMEANS BACKGROUND OF THE INVENTION The invention pertains to vehicle seatassemblies having a cushioned seat which is resiliently suspended forproviding a comfortable ride for the operator. An air spring or the likeprovides the resilient suspension for the seat, and an example of thisgeneral type of parallel arm seat suspension is shown in US. Pat. No.3,215,386 which issued on Nov. 2, 1965 and is entitled Pneumatic SeatSupport. The US. Pat. No. 3,150,855 to Carter et al which issued Sept.29, 1964, entitled Resilient Suspension for Vehicle Seat, also disclosesa parallel arm linkage arrangement for insuring that the seat maintainsa constant attitude to the vehicle regardless of its vertical position,and in addition, a shock absorber or damper is provided to damp thespring action of the air cylinder and thus retard excessive bouncing ofthe seat when operating in roug terrain.

Another example of a prior art device of this general type is shown inthe U.S. Pat. No. 3,558,094 which issued on Jan. 26, 1971 to Radke andentitled Vehicle Seat having Optimum Angular Motion Characteristics.

SUMMARY OF THE INVENTION The present invention provides a resilientlysuspended vehicle seat for earth working or agricultural vehicles or thelike and which seat has cushioning means, for example such as an airspring. In addition the seat assembly provided by the present inventionincludes damping means which are so constructed and arranged so that itcan be easily adjusted to provide different degrees of hardness orsoftness to the operators ride, and which damping means also acts withessentially constant force on the seat regardless of the selectedvertical position to which it has been moved and regardless of thevertical position of the seat when swinging or bouncing as in use inrough terrain. The constantly acting damping means provides aparticularly comfortable ride and one which will not have hard bottomingor hard topping or a reduction in damping at the top.

The invention also provides the seat assembly of the above type havingmeans for easily locking out the resilient means whereby the seat islocked in a solid" ride position and essentially at the midpoint of itsotherwise vertically swinging movement.

Another aspect of the invention provides a seat assembly of the abovetype having means for readily adjusting the vertical position of theseat initially so as to accommodate operators of different sizes.

Furthermore the present invention provides a seat of the above typehaving a cushioned seat that is pivoted at its front edge to therebymaintain the front edge of the seat at a constant point and therebymaintains the operators feet a constant distance relative to the ground.Furthermore, the seat assembly provided by the present invention hasoptimum seat back rotation about the H point of the human body tothereby minimize vertical back scrubbing and undesirable fore and aftmovement.

These and other objects and advantages will appear hereinafter as thisdisclosure progresses, reference being had to the accompany drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a left side elevational viewshowing a vehicle seat made in accordance with the present invention andshowing certain hidden parts in dotted lines, the seat being in thevertically lower position;

FIG. 2 is a side elevational view of certain parts shown in FIG. 1,namely the seat support and the limit stop rod associated with the seatsupport, and also 0 showing the tie rod lock-out means;

FIG. 3 is a side elevational view of other parts shown in FIG. 1, namelythe damper and its connecting link to the seat, which will allowadjusting the softness of the ride;

FIG. 4 is a transverse, sectional view taken along line 4--4 in FIG. 1,certain parts being shown as broken away or removed for the sake ofclarity;

FIG. 5 is a transverse, sectional view taken along line 55 in FIG. 4,certain sections being shown as broken away or removed for the sake ofclarity;

FIG. 6 is a partial, front elevational view of the seat shown in FIG. 1and showing certain hidden parts in dotted lines;

FIG. 7 is a side elevational view taken generally along the line 77 inFIG. 6, certain parts being shown as broken away or removed for the sakeof clarity;

FIG. 8 is a transverse sectional view taken generally along the line 8-8in FIG. 7 and showing the damper adjustment means and also the seatlock-out means;

FIG. 9 is a left side elevational view of a portion of FIG. 6 and issimilar to the showing of FIG. 7, except that certain parts have beenbroken away or removed to show more clearly the damper adjusting meansby means of which the softness of the seat ride can be varied;

FIG. 9a is a view somewhat similar to FIG. 9, but showing the damperadjustment means when shifted to a position in which the softest ride isobtained;

FIG. 10 is a perspective view of the cam shown in FIG. 9;

FIG. 11 is a perspective view of the seat and taken generally from theright rear upper side of the seat, certain parts being shown as brokenaway or removed for the sake of clarity, and other parts shown asremoved from its associated part;

FIG. 12 is a fragmentary, perspective view of the seat, the view beingtaken from the left rear upper portion of the seat, certain parts beingshown as broken away or removed for the sake of clarity;

FIG. 13 is a perspective view of the seat, the view being takengenerally from the lower front left side of the seat and showing theseat when shifted to the upper position;

FIG. 14 is a left elevational view of a portion of the seat and showingthe air cylinder for cushioning the seat;

FIG. 15 is a rear view and taken generally along the line 15-15 in FIG.14.

DESCRIPTION OF A PREFERRED EMBODIMENT Carriage and Parallel Arm LinkageAdjustment A vertically shiftable seat carriage is swingably mounted byparallel arm linkage so that it can rise and fall at a constantattitude. Adjustment means are also provided for fixedly adjusting thecarriage in any one of a selected number of vertical positions. Theadjustment can be readily made by a handle located at the forwardportion of the carriage and within easy reach of the operator.

The seat assembly includes a base in the form of two cast base sections1 and 2 which are spaced apart from one another and extend generallyupwardly. These base sections have apertures 3 in their flange footportion by means of which they can be bolted or otherwise secured to thevehicle body (not shown). A seat carriage 5 is fabricated from heavysheet steel and is of generally U-shaped configuration having a frontwall 6, a right side wall 7 and a left side wall 8. Side walls 7 and 8extend rearwardly of the front wall and are in general parallelism withone another. The carriage is vertically and adjustably mounted on thebase for vertically positioning the seat S connected thereto, and thismounting is by means of two pairs of parallel arms, one pair located oneach side. One pair of arms 10 and 11 on the left side are connected tothe base by shafts 12 and 13, respectively, and are then pivotallyconnected at their upper ends of the side wall 8 of the carriage bymeans ofthe bolt means 14 and 15, respectively, which extend throughholes 14a and 15a in the side wall 8 of the carriage. The other pair ofarms and 21 on the right hand side of the seat are connected to the baseby shaft 22 and 23, respectively and are then pivotally connected attheir upper ends to the right side 7 of the carriage by the bolt means24 and 25 which extend through holes 24a and 25a in the carriage wall 7.

The arms 10, l1 and 20, 21 form a parallel linkage connection betweenthe base and the carriage so that the seat is maintained at a constantattitude relative to the vehicle, regardless of the vertical positionthereof.

Means are provided for manually adjusting the vertical position of thecarriage 5 relative to the base and this includes a pair of adjustmentplates 26 and 27, one pivotally mounted on each side of the carriage 5on their respective bolt means 14 and 24. The front end of theadjustment plates 26 and 27 are rigidly connected together by means ofthe handle 30 which is welded to the front ends of the adjustment platesand extends thereacross. The adjustment plates have a series of notches31, 32, 33 and 34 along their rearward sides and these notches areadapted to receive fixed means in the form of the extending portions ofshafts 13 and 23 which, as previously mentioned, also form the pivotconnection between some of the parallel arms and the bases. In thismanner, the operator, by swinging the forwardly extending portion 30a ofthe handle 30, can cause the adjustment plates to pivot about their boltmeans 14 and 24, and thereby change the particular notch in which theshafts 13 and 23 are located. For example, as shown in FIG. 1, theshafts I3 and 23 are located in the rearmost notch 31 placing the seatin the lowermost position. The other extreme seat position is shown inFIGS. 11 and 12 wherein the shafts 13 and 23 are located in theforwardmost notches 34 of the adjustment plates, and this places thecarriage and seat in the uppermost position.

The carriage 5 also has a centrally located, channel shaped bracket 35(FIG. 15) welded to the inside ofits front wall 6, and a pair ofupwardly extending lugs 36 are in turn welded to and extend upwardlyfrom the bracket 35, a tube 37 is welded to and between lugs 36 andforms a mounting for a pivot bolt 39 on which a sheet steel fabricatedseat pivot plate 40 is pivoted. The seat S is thus pivoted on the pivotbolt 39 to the upwardly extending lugs 36 of the upper carriage 5.

The carriage also has a mounting base 41 welded or otherwise fixedthereto, as between the channel brackets 35. This base 41 forms amounting for the lower end of an air cylinder unit AC (FIG. 1, 14 and15) to be described.

The seat assembly SA is constructed and mounted on the upper carriage 5as follows. A metal sheet base 50, for supporting the seat cushion 50a,has a pair of seat supports 51 and 52 which are located on oppositesides and complement one another. These supports each have a lowerportion 51a and 520 between which is secured a retainer 53 for the upperend of the previously mentioned air cylinder unit AC. The supports 51and 52 also each have an upwardly extending portion 51b and 52b,respectively, to which the seat back 57 is pivoted, as at 55. The lowerend of the seat back 57 is also pivotally connected at each side to therear ends of a pair of seat links 58 and 59. (FIGS. 1, 6, 11, 12 and 13)which in turn are pivotally mounted, adjacent their front ends to thecarriage by bolt means 15 and 25, respectively. The large seat links 58and 59 are rigidly secured together adjacent their rear ends by thecross brace 60 welded therebetween. The rear ends of seat links 58 and59 are pivotally connected by short links 61 and 62 to a tubular member63 extending between and connected to the lower ends 57a of the seatback 57.

Thus the seat supports 51 and 52 freely support the seat S on theirhorizontal surfaces 510 and the seat back 57 is pivoted to the upperends of the seat supports at the l-l point of the operator. The seatlinks 58, 59 are pivotally connected at their front ends to the carriageand at their other ends to the seat back by means of the linkageconnection 61, thereby causing the seat back to oscillate about thepoint of pivotal connection between the seat supports 51, 52 and theseat back 57.

I In this manner, as the seat rises and falls, the back 57 is maintainedat a constant attitude and at the proper position for comfort of theoperator, more specifically, the seat back 57 pivots about its l-l"point 55. This provides optimum back rotation of the back seat portionabout the H point of the human body to thereby minimize excess backscrub and unwanted fore and aft movement.

The air cylinder unit AC is of itself conventional in character and maybe of the type manufactured by Goodyear Rubber Co. and commonly referredto as an air spring", and having a tubular rubber sleeve 65 (FIGS. 14and 15) which rolls over a piston 66. This air spring" acts between theseat S and the carriage 5 to form a resilient cushion for the seat.

Adjustable Damper Means Means will now be described for adjusting theeffectiveness of a seat damper D so that the character of the ride maybe varied, that is to say, the degree of softness or hardness of theride may be selected.

In any of the selected positions, the damper acts with constant force,in resisting downward and upward seat movement, regardless of thevertical position to which the seat swings. That is to say, the dampingeffect of the damper is substantially constant regardless of whether theseat is at the top or bottom of its bouncing or swinging movement.

The damper means includes a damper D which is of conventional characterand may be of the fluid type shock absorber having a valve which metersthe flow of fluid from one of its ends to the other.

The action of the damper may be selectively adjusted to provide thedesired degree of softness of the ride, as follows.

The damper D is pivotally mounted at its lower end to the lower end ofcarriage 5 by bracket 42, and has a pivotal connection at its upper end,by a pin 69, with an intervening, channel shaped link 70 (FIG. 9), whichin turn is pivoted at its other end to the seat plate 40. Thus thedamper is pivotally connected to the seat through the link 70.

Means are provided for shifting the pivotal connection 69 as follows. Asliding link 72 is also pivotally connected at one end to the pin 69 andthe other end of link 72 is pivotally connected on a stub shaft 73 whichextends through a slot 49 in carriage wall 7. A nut 74 is threaded onthe outer end of the shaft 73 and holds the shaft captive in the slot49.

The shaft can be locked in any one of a number of positions along theslot 49, thereby changing the link of force through which the damper Dacts on against' movement of the seat. This locking is accomplished byan arm 75 fixed on and connecting the shaft 73 to the damper adjustinghandle 48 which in turn is held captive in any one of a number of thenotches 43, 44, 45, 46, or 47 in the carriage wall 7.

When the handle 48 is in the notch 46 (FIGS. 9 and II) the line of forceof the damper D is indicated by line F, which acts through the momentarm MA in respect to the point of seat pivot 39. This is the hardest"seat adjustment position, in other words, where the firmest ride isprovided by the damper D.

When the handle 48 is shifted to the foremost notch 43, the line offorce through which the damper acts is indicated by F1 in FIG. 9a,acting through moment arm MAI. In this position, a softest ride isobtained because the vector product of F1 and MAI is less than thevector product of F and MA. In other words, the line of action of thedamper in the FIG. 9 position is a greater perpendicular distance frompoint 39 than when the damper is in the FIG. 9a, position.

However, regardless of the position to which the damper has beenadjusted for any one adjustment, the damper acts with constanteffectiveness against seat movement because the slide link 72 swingsabout an arc described by the dotted line A in FIG. 9, and moreparticularly, the point of pivotal connection of the damper D to the arm72 moves in this are A which practically maintains the line of force ofthe damper a constant distance from 39 throughout the vertical swingingmovement of the tractor seat S.

In regard to the maximum amount of swinging or vertical movement of thetractor seat, this is determined by the lower stop LS (FIG. 2) and theupper stop US which are formed on the seat support members 51 and 52,and which stops abut against the limit stop rod 76 secured rigidly toand between the walls 7 and 8 of the carriage.

Seat Lock-Out Means Lock-out means are provided for locking the seat ina solid or non-cushion position during operation in particularly roughconditions. This means acts to lock the seat in its approximate midpointof travel in a vertical direction. The lock-out position is engaged withthe same handle 48 which is used to adjust the effectiveness of thedamper D. When the handle 48 is located in the deepest and most rearwardnotch 47 (FIGS. 7 and 1 I the seat is in the locked position.

More specifically, a cam 77 (FIGS. 9, 10 and 12) is secured, as bywelding, to the inner end of shaft 73 and is engagable with a pin 78(FIGS. 8, 9 and 11) fixed intermediate the length of a lock-out link 79.The link 79 is journalled at its lower end on the bolt means 25; asimilar link 79a (FIG. 11) is joumalled on the other side on shaft 15.The links 79 and 79a are connected together by a U-shaped tie rod 80,whereby they swing in unison. When the operator shifts handle 48 intothe rear notch 47, this movement causes similar rearward shifting of theassociated sliding link 72, which carries with it the shaft 73 and itscam 77. As a result, the cam 77 abuts against pin 78 on link 79,swinging link 79 rearwardly, shifting the tie rod portions 80a and 80binto lock-out recesses 82 (FIGS. 1 and 2) in the rigid seat supports 51and 52. In this position the seat is locked against movement.

RESUME By means of the present invention, a seat assembly has beenprovided wherein the action of the damping means can be readily variedto provide different degrees of hardness or softness to the rideregardless of the type of ride selected. This damping means acts withessentially constant force in its damping action on the seat andregardless of the vertical position to which the seat bounces or swingsduring operation. Furthermore, the resilient means can be readily lockedout of operation with some handle used to adjust the softness orhardness of the ride, and this locked out position occurs generally atthe vertical midpoint through which the seat would otherwise swing.

In addition, the seat assembly of the present invention provides areadily adjustable means to adjust the vertical height of the seat foroperators of different size, and this adjustment is effected by a simpleswinging action of the conveniently located lever.

The seat assembly provided by the present invention also provides anon-linear suspension type seat wherein the operator's knees aremaintained at a constant position regardless of the seat adjustmentselected. Furthermore, the seat back rotates about the I-I" point of thehumanbody to thereby eliminate undesirable fore and aft movement of theback or undesirable back scrubbing on the operator in a verticaldirection.

We claim:

1. A resiliently suspended vehicle seat for vehicles and comprising; avertically shiftable carriage, means for swingably mounting saidcarriage in a vertical direction, a seat having a pivotal mountingadjacent its forward end to said carriage, damper means pivotallyconnected between said carriage and said seat and including a damper anda link having a pivotal connection with said damper, means foradjustably shifting said pivotal connection whereby the effective momentarm of said damper in respect to said seat pivotal mounting can bevaried, said means for shifting said pivotal connection also beingshiftably and swingably mounted on said carriage whereby said pivotalconnection swings in a generally flat arc which is generally coincidentwith the line of force of said damper as said tractor seat rises andfalls, whereby the damper has a substantially constant damping effect onsaid seat regardless of the vertical swinging movement of said seat.

2. The seat set forth in claim 1 wherein said means for shifting saidpivotal connection includes a shiftable link having a handle attachedthereto, and a series of recesses in said carriage into which saidhandle can be selectively positioned.

3. The seat set forth in claim 1 further characterized in that saidmeans for shifting said pivotal connection has a cam connected therewithand a lock-out means shiftably mounted on said carriage for shifting toa position locking said seat in a fixed position, said cam beingengagable with said lock out means so as to cause shifting thereof tosaid position when said handle is moved to a predetermined position.

4. The seat set forth in claim 2 further characterized in that saidmeans for shifting said pivotal connection has a cam connected therewithand a lock-out means shiftably mounted on said carriage for shifting toa position locking said seat in a fixed position, said cam beingengagable with said lock out means so as to cause shifting thereof tosaid position when said means for shifting said pivotal connection ismoved to a predetermined position.

5. A vertically adjustable vehicle seat assembly comprising a mountingbase member, a vertically shiftable carriage, parallel arm linkagebetween said base member and said carriage for vertically positioningsaid carriage in any one of a number of selected vertical positions; apair of adjustment plates pivotally mounted to said carriage, one oneach side of said carriage; a series of recesses in said adjustmentplates, fixed means on said base member and engagable in any of saidrecesses when said carriage is shifted to different vertical positions,and handle means connected with said adjustment plates for swinging thelatter whereby any one of said recesses in said adjustment plates may beengaged by said fixed means carried on said base member, whereby saidcarriage may be selectively held in any one of a number of positions towhich it is vertically shifted by said parallel arm linkage.

6. The seat assembly set forth in claim 5 further characterized in thatsaid carriage comprises a generally U-shaped member having two sideportions and a bight portion connected therebetween, said handle meanslocated across the bight portion, and said pair of adjustment plates arepivotally mounted to said carriage adjacent the bight portion, saidadjustment plates extending rearwardly alongside said side portions andhaving said recesses adjacent the rear ends of said adjustment plates.

7. The seat assembly set forth in claim 5 including a seat pivotallyconnected adjacent its forward end to a forward portion of saidcarriage.

8. The seat assembly set forth in claim 6 including a seat pivotallyconnected adjacent its forward end to a forward portion of saidcarriage.

9. A vertically adjustable vehicle seat assembly comprising a mountingbase member, a vertically shiftable carriage, parallel arm linkagebetween said base member and said carriage for vertically positioningsaid carriage in any one of a number of selected vertical positions; aseat having a pivotal mounting adjacent its forward end to saidcarriage, damper means pivotally connected between said carriage andsaid seat and including a damper and a link having a pivotal connectionwith said damper, means for adjustably shifting said pivotal connectionwhereby the effective moment arm of said damper in respect to said seatpivotal mounting can be varied, said means for shifting said pivotalconnection also being shiftably and swingably mounted on said carriageso that said pivotal connection swings in a generally flat are which isgenerally coincident with the line of force of said damper as saidtractor seat rises and falls, whereby the damper has a substantiallyconstant damping effect on downward movement of said seat; a pair ofadjustment plates pivotally mounted to said carriage, one on each sideof said carriage; a series of recesses in said adjustment plates, fixedmeans on said base member and engagable in any one of said recesses whensaid carriage is shifted to different vertical positions, and handlemeans connected with said adjustment plates for swinging the latterwhereby any one of said recesses in said adjustment plates may beengaged by said fixed means carried on said base member, whereby saidcarriage may be selectively held in any one of a number of positions towhich it is vertically shifted by said parallel arm linkage.

10. The seat assembly set forth in claim 9 further characterized in thatsaid carriage comprises a generally U-shaped member having two sideportions and a bight portion connection therebetween, said handlemeanslocated across the bight portion, and said pair of adjustmentplates are pivotally mounted to said carriage adjacent the bightportion, said adjustment plates extending rearwardly alongside said sideportions and having said recesses adjacent the rear ends of saidadjustment plates.

11. A resiliently suspended vehicle seat assembly comprising; a supportbase, a vertically shiftable carriage, parallel arm linkage meanspivotally connected between said base and said carriage for swingablymoving said carriage at a constant attitude in a vertical direction, aseat having a pivotal mounting adjacent its forward end to said carriagefor vertical swinging relative thereto, a pair of seat supports on whichsaid seat freely rests, resilient cushioning means between said carriageand said seat supports for cushioning the downward vertical swinging ofsaid seat and supports, a seat back pivotally mounted to said seatsupports, a pair of seat links pivotally connected at one end to saidcarriage and at their other end having a link connection with said seatback whereby said seat back rotates about the point of its said pivotalmounting to said seat supports during vertical swinging of said seat.

12. The seat assembly set forth in claim 11 further characterized inthat said seat supports have upper and lower stop limits, and stop meansmounted on said carriage and engagable by said stop limits to define theupper and lower limits to which said seat supports can move.

13. A vertically adjustable vehicle seat assembly comprising a mountingbase member, a vertically shiftable carriage, parallel arm linkagebetween said base member and said carriage for vertically positioningsaid carriage at a constant attitude and in any one of a number ofselected vertical positions; a seat having a pivotal mounting adjacentits forward end to said carriage for vertical swinging relative thereto,a pair of seat supports on which said seat freely rests, resilientcushioning means between said carriage and said seat supports forcushioning the downward vertical swinging of said seat and supports, aseat back pivotally mounted to said seat supports, a pair of seat linkspivotally connected at one end to said carriage and at their other endhaving a link connection with said seat back whereby said seat backrotates about the point of its said pivotal mounting to said seatsupports during vertical swinging of said seat; a pair of adjustmentplates pivotally mounted to said carriage, one on each side of saidcarriage; a series of recesses in said adjustment plates, fixed means onsaid base member and engagable in any one of said recesses when saidcarriage is shifted to different vertical positions, and handle meansconnected with said adjustment plates for swinging the latter wherebyany one of said recess in said adjustment plates may be engaged by saidfixed means carried on said base member, whereby said carriage may beselectively held in any one of a number of positions to which it isvertically shifted by said parallel arm linkage.

14. The seat assembly set forth in claim 13 further characterized inthat said carriage comprises a generally U-shaped member having two sideportions and a bight portion connected therebetween, said handle meanslocated across the bight portion, and said pair of adjustment plates arepivotally mounted to said carriage adjacent the bight portion, saidadjustment plates extending rearwardly alongside said side por- I tionsand having recesses adjacent the rear ends of said adjustment plates.

15. The seat assembly set forth in claim 13 further characterized inthat said seat supports have upper and lower stop limits, and stop meansmounted on said carriage and engagable by said stop limits to define theupper and lower limits to which said seat supports can move.

16. A vertically adjustable vehicle seat assembly comprising a mountingbase member, a vertically shiftable carriage, parallel arm linkagebetween said base member and said carriage for vertically positioningsaid carriage at a constant attitude and in any one of a number ofselected vertical positions; a seat having a pivotal mounting adjacentits forward end to said carriage, damper means pivotally connectedbetween said carriage and said seat and including a damper and a linkhaving a pivotal connection with said damper, means for adjustablyshifting said pivotal connection ill whereby the effective moment arm ofsaid damper in respect to said seat pivotal mounting can be varied, saidmeans for shifting said pivotal connection also being shiftably andswingably mounted on said carriage to swing said pivotal connection in agenerally flat arc which is generally coincident with the line of forceof said damper as said tractor seat rises and falls, whereby the damperhas a substantially constant damping effect on said seat regardless ofthe vertical swingingmovement of sa1d seat; a seat having a pivotalmounting adjacent its forward end to said carriage for vertical swingingrelative thereto, a pair of seat supports on which said seat freelyrests, resilient cushioning means between said carriage and said seatsupports for cushioning the downward vertical swinging of said seat andsupports, a seat back pivotally mounted to said seat supports, a pair ofseat links pivotally connected at one end to said carriage and at theirother end having a link connection with said seat back whereby said seatback rotates about the point of its said pivotal mounting to said seatsupports during vertical swinging of said seat; a pair of adjustmentplates pivotally mounted to said carriage, one on each side of saidcarriage; a series of recesses in said adjustment plates, fixed means onsaid base member and engagable in any one of said recesses when saidcarriage is shifted to different vertical positions, and handle meansconnected with said adjustment plates for swinging the latter wherebyany oneof said recesses in said adjustment plates may be engaged by saidfixed means carried on said base member, whereby said carriage may beselectively held in any one of a number of positions to which it isvertically shifted by said parallel arm linkage.

17. The seat assembly set forth in claim 16 further characterized inthat said carriage comprises a generally U-shaped member having two sideportions and a bight portion connected therebetween, said handle meanslocated across the bight portion, and said pair of adjustment plates arepivotally mounted to said carriage adjacent the bight portion, saidadjustment plates extending rearwardly alongside said side portions andhaving said recesses adjacent the rear ends of said adjustment plates.

18. The seat assembly set forth in claim 16 further characterized inthat said seat supports have upper and lower stop limits, and stop meansmounted on said carriage and engagable by said stop limits to define theupper and lower limits to which said seat supports can move.

1Q. The seat assembly set forth in claim 17 further characterized inthat said seat supports have upper and lower stop limits, and stop meansmounted on said carriage and engagable by said stop limits to define theupper and lower limits to which said seat supports can move.

1. A resiliently suspended vehicle seat for vehicles and comprising; avertically shiftable carriage, means for swingably mounting saidcarriage in a vertical direction, a seat having a pivotal mountingadjacent its forward end to said carriage, damper means pivotallyconnected between said carriage and said seat and including a damper anda link having a pivotal connection with said damper, means foradjustably shifting said pivotal connection whereby the effective momentarm of said damper in respect to said seat pivotal mounting can bevaried, said means for shifting said pivotal connection also beingshiftably and swingably mounted on said carriage whereby said pivotalconnection swings in a generally flat arc which is generally coincidentwith the line of force of said damper as said tractor seat rises andfalls, whereby the damper has a substantially constant damping effect onsaid seat regardless of the vertical swinging movement of said seat. 2.The seat set forth in claim 1 wherein said means for shifting saidpivotal connection includes a shiftable link having a handle attachedthereto, and a series of recesses in said carriage into which saidhandle can be selectively positioned.
 3. The seat set forth in claim 1further characterized in that said means for shifting said pivotalconnection has a cam connected therewith and a lock-out means shiftablymounted on said carriage for shifting to a position locking said seat ina fixed position, said cam being engagable with said lock out means soas to cause shifting thereof to said position when said handle is movedto a predetermined position.
 4. The seat set forth in claim 2 furthercharacterized in that said means for shifting said pivotal connectionhas a cam connected therewith and a lock-out means shiftably mounted onsaid carriage for shifting to a position locking said seat in a fixedposition, said cam being engagable with said lock out means so as tocause shifting thereof to said position when said means for shiftingsaid pivotal connection is moved to a predetermined position.
 5. Avertically adjustable vehicle seat assembly comprising a mounting basemember, a vertically shiftable carriage, parallel arm linkage betweensaid base member and said carriage for vertically positioning saidcarriage in any one of a number of selected vertical positions; a pairof adjustment plates pivotally mounted to said carriage, one on eachside of said carriage; a series of recesses in said adjustment plates,fixed means on said base member and engagable in any of said recesseswhen said carriage is shifted to different vertical positions, andhandle means connected with said adjustment plates for swinging thelatter whereby any one of said recesses in said adjustment plates may beengaged by said fixed means carried on said base member, whereby saidcarriage may be selectively held in any one of a number of positions towhich it is vertically shifted by said parallel arm linkage.
 6. The seatassembly set forth in claim 5 further characterized in that saidcarriage comprises a generally U-shaped member havIng two side portionsand a bight portion connected therebetween, said handle means locatedacross the bight portion, and said pair of adjustment plates arepivotally mounted to said carriage adjacent the bight portion, saidadjustment plates extending rearwardly alongside said side portions andhaving said recesses adjacent the rear ends of said adjustment plates.7. The seat assembly set forth in claim 5 including a seat pivotallyconnected adjacent its forward end to a forward portion of saidcarriage.
 8. The seat assembly set forth in claim 6 including a seatpivotally connected adjacent its forward end to a forward portion ofsaid carriage.
 9. A vertically adjustable vehicle seat assemblycomprising a mounting base member, a vertically shiftable carriage,parallel arm linkage between said base member and said carriage forvertically positioning said carriage in any one of a number of selectedvertical positions; a seat having a pivotal mounting adjacent itsforward end to said carriage, damper means pivotally connected betweensaid carriage and said seat and including a damper and a link having apivotal connection with said damper, means for adjustably shifting saidpivotal connection whereby the effective moment arm of said damper inrespect to said seat pivotal mounting can be varied, said means forshifting said pivotal connection also being shiftably and swingablymounted on said carriage so that said pivotal connection swings in agenerally flat arc which is generally coincident with the line of forceof said damper as said tractor seat rises and falls, whereby the damperhas a substantially constant damping effect on downward movement of saidseat; a pair of adjustment plates pivotally mounted to said carriage,one on each side of said carriage; a series of recesses in saidadjustment plates, fixed means on said base member and engagable in anyone of said recesses when said carriage is shifted to different verticalpositions, and handle means connected with said adjustment plates forswinging the latter whereby any one of said recesses in said adjustmentplates may be engaged by said fixed means carried on said base member,whereby said carriage may be selectively held in any one of a number ofpositions to which it is vertically shifted by said parallel armlinkage.
 10. The seat assembly set forth in claim 9 furthercharacterized in that said carriage comprises a generally U-shapedmember having two side portions and a bight portion connectiontherebetween, said handle means located across the bight portion, andsaid pair of adjustment plates are pivotally mounted to said carriageadjacent the bight portion, said adjustment plates extending rearwardlyalongside said side portions and having said recesses adjacent the rearends of said adjustment plates.
 11. A resiliently suspended vehicle seatassembly comprising; a support base, a vertically shiftable carriage,parallel arm linkage means pivotally connected between said base andsaid carriage for swingably moving said carriage at a constant attitudein a vertical direction, a seat having a pivotal mounting adjacent itsforward end to said carriage for vertical swinging relative thereto, apair of seat supports on which said seat freely rests, resilientcushioning means between said carriage and said seat supports forcushioning the downward vertical swinging of said seat and supports, aseat back pivotally mounted to said seat supports, a pair of seat linkspivotally connected at one end to said carriage and at their other endhaving a link connection with said seat back whereby said seat backrotates about the point of its said pivotal mounting to said seatsupports during vertical swinging of said seat.
 12. The seat assemblyset forth in claim 11 further characterized in that said seat supportshave upper and lower stop limits, and stop means mounted on saidcarriage and engagable by said stop limits to define the upper and lowerlimits to which said seat supports can move.
 13. A vertically adjustablevehicle seat assembly comprising a mounting base member, a verticallyshiftable carriage, parallel arm linkage between said base member andsaid carriage for vertically positioning said carriage at a constantattitude and in any one of a number of selected vertical positions; aseat having a pivotal mounting adjacent its forward end to said carriagefor vertical swinging relative thereto, a pair of seat supports on whichsaid seat freely rests, resilient cushioning means between said carriageand said seat supports for cushioning the downward vertical swinging ofsaid seat and supports, a seat back pivotally mounted to said seatsupports, a pair of seat links pivotally connected at one end to saidcarriage and at their other end having a link connection with said seatback whereby said seat back rotates about the point of its said pivotalmounting to said seat supports during vertical swinging of said seat; apair of adjustment plates pivotally mounted to said carriage, one oneach side of said carriage; a series of recesses in said adjustmentplates, fixed means on said base member and engagable in any one of saidrecesses when said carriage is shifted to different vertical positions,and handle means connected with said adjustment plates for swinging thelatter whereby any one of said recess in said adjustment plates may beengaged by said fixed means carried on said base member, whereby saidcarriage may be selectively held in any one of a number of positions towhich it is vertically shifted by said parallel arm linkage.
 14. Theseat assembly set forth in claim 13 further characterized in that saidcarriage comprises a generally U-shaped member having two side portionsand a bight portion connected therebetween, said handle means locatedacross the bight portion, and said pair of adjustment plates arepivotally mounted to said carriage adjacent the bight portion, saidadjustment plates extending rearwardly alongside said side portions andhaving recesses adjacent the rear ends of said adjustment plates. 15.The seat assembly set forth in claim 13 further characterized in thatsaid seat supports have upper and lower stop limits, and stop meansmounted on said carriage and engagable by said stop limits to define theupper and lower limits to which said seat supports can move.
 16. Avertically adjustable vehicle seat assembly comprising a mounting basemember, a vertically shiftable carriage, parallel arm linkage betweensaid base member and said carriage for vertically positioning saidcarriage at a constant attitude and in any one of a number of selectedvertical positions; a seat having a pivotal mounting adjacent itsforward end to said carriage, damper means pivotally connected betweensaid carriage and said seat and including a damper and a link having apivotal connection with said damper, means for adjustably shifting saidpivotal connection whereby the effective moment arm of said damper inrespect to said seat pivotal mounting can be varied, said means forshifting said pivotal connection also being shiftably and swingablymounted on said carriage to swing said pivotal connection in a generallyflat arc which is generally coincident with the line of force of saiddamper as said tractor seat rises and falls, whereby the damper has asubstantially constant damping effect on said seat regardless of thevertical swinging movement of said seat; a seat having a pivotalmounting adjacent its forward end to said carriage for vertical swingingrelative thereto, a pair of seat supports on which said seat freelyrests, resilient cushioning means between said carriage and said seatsupports for cushioning the downward vertical swinging of said seat andsupports, a seat back pivotally mounted to said seat supports, a pair ofseat links pivotally connected at one end to said carriage and at theirother end having a link connection with said seat back whereby said seatback rotates about the point of its said pivotal mounting to said seatsupports durIng vertical swinging of said seat; a pair of adjustmentplates pivotally mounted to said carriage, one on each side of saidcarriage; a series of recesses in said adjustment plates, fixed means onsaid base member and engagable in any one of said recesses when saidcarriage is shifted to different vertical positions, and handle meansconnected with said adjustment plates for swinging the latter wherebyany one of said recesses in said adjustment plates may be engaged bysaid fixed means carried on said base member, whereby said carriage maybe selectively held in any one of a number of positions to which it isvertically shifted by said parallel arm linkage.
 17. The seat assemblyset forth in claim 16 further characterized in that said carriagecomprises a generally U-shaped member having two side portions and abight portion connected therebetween, said handle means located acrossthe bight portion, and said pair of adjustment plates are pivotallymounted to said carriage adjacent the bight portion, said adjustmentplates extending rearwardly alongside said side portions and having saidrecesses adjacent the rear ends of said adjustment plates.
 18. The seatassembly set forth in claim 16 further characterized in that said seatsupports have upper and lower stop limits, and stop means mounted onsaid carriage and engagable by said stop limits to define the upper andlower limits to which said seat supports can move.
 19. The seat assemblyset forth in claim 17 further characterized in that said seat supportshave upper and lower stop limits, and stop means mounted on saidcarriage and engagable by said stop limits to define the upper and lowerlimits to which said seat supports can move.